Creating and Editing Files with Vim

Vim is a powerful terminal-based text editor commonly used in Unix-like environments. It can be intimidating for beginners, but it's a valuable tool once you get the hang of it. This crash course will guide you through creating and editing a file using Vim.

Creating a New File

1. Open a Terminal: Launch your terminal or command prompt.

2. Create a New File: To create a new file or open an existing one, type the following command, replacing filename with your desired file name:

   vim filename

Entering Vim

After running the vim command, Vim will open with the new file. You'll see the empty document with a status line at the bottom.

Editing a File in Vim

Vim operates in different modes: Normal, Insert, and Command-line. Here's how to navigate and edit text in each mode:

Normal Mode (moving around document)

Use the arrow keys or H, J, K, L keys to navigate around the document.

• i: Enter Insert mode before the cursor.
• I: Enter Insert mode at the beginning of the line.
• a: Enter Insert mode after the cursor.
• A: Enter Insert mode at the end of the line.
• o: Open a new line below the current line and enter Insert mode.
• O: Open a new line above the current line and enter Insert mode.
• x: Delete the character under the cursor.
• dd: Delete the entire line.
• 2dd: Delete 2 lines.
• dG: Delete all lines from here until end of file.
• yy: Yank (copy) the current line.
• 2yy: copy 2 lines
• p: Paste the yanked or deleted text after the cursor.
• w: move to next word

Insert Mode (Esc and then i goes into this mode -- used to add new text)

In Insert mode, you can type and edit text as you would in a regular text editor. Press Esc to return to Normal mode.

Command Mode (Esc and then : goes into this mode -- used to save, quit, etc)

• To save your changes and exit Vim, press Esc to ensure you're in Normal mode, and then type :w and press Enter.
• To quit Vim without saving changes, press Esc to ensure you're in Normal mode, and then type :q! and press Enter.
• To save changes and quit Vim, type :wq and press Enter.
• To search for text, press Esc to return to Normal mode, then type / followed by the search term and press Enter. Use n to go to the next match and N to go to the previous match.

Examples:

• ESC and :w will save
• ESC and then :wq will save and quit Vim

How to create shell script

Open a Text Editor

Use a text editor like Vim or nano to create your script file. For this example, let's call it myscript.sh.

vim myscript.sh

Shebang Line

The first line of your script should specify the shell interpreter. In most cases, you'll use #!/bin/bash to indicate that this is a Bash script.

#!/bin/bash

Write Your Script

Add your Bash commands below the shebang line. Here's a simple example that prints "Hello, World!" to the terminal:

echo "Hello, World!"

Save the file (esc and then :wq in Vim)

Make It Executable

You need to make your script executable. Use the chmod command to give it execute permissions:

chmod +x myscript.sh

Run Your Script

To execute your script, simply type its name in the terminal:

./myscript.sh Ensure that you are in the same directory as your script, or provide the full path if it's located elsewhere.

Note: you can also call the script without it being executable by calling the interpreter and then the script as an argument.

sh ./myscript.sh

Comments and Documentation

Good scripts have comments to explain what each part does. Use # to add comments in your script

# This is a simple script that prints a greeting
echo "Hello, World!"

Variables

You can use variables to store and manipulate data. Here's an example:

name="John"
echo "Hello, $name!"

User Input

You can prompt the user for input using the read command:

echo "What's your name?"
read name
echo "Hello, $name!"

Conditional Statements

Use if, elif, and else to create conditional statements:

age=18
if [ "$age" -ge 18 ]; then
    echo "You are an adult."
else
    echo "You are not yet an adult."
fi

Loops

You can use loops like for and while for repetitive tasks:

for i in {1..5}; do
    echo "Iteration $i"
done

Functions

You can define functions to organize your code:

greet() {
    echo "Hello, $1!"
}
greet "Alice"
greet "Bob"

Error Handling

You can handle errors with exit codes and error messages:

if [ ! -f myfile.txt ]; then
    echo "Error: myfile.txt does not exist."
    exit 1
fi